Place the bacon in a large, deep skillet, and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain the bacon slices on a paper towel-lined plate. Let cool, then crumble into small pieces.
Mix bacon and feta together in small bowl.
Cut a 2 to 3 inch slit lengthwise in the side of the chicken breast creating a pocket, and fill with mixture. Secure shut with toothpicks.
Place chicken in slow cooker, then add tomatoes and basil.
Cook on High until chicken is no longer pink in the middle, about three hours.